Most people detect a distinct sulfurous odor in their urine shortly after eating asparagus. However, there are some who seemingly do not notice the unpleasant odor.

Up until now, it has been unclear whether this is because these individuals do not produce the odor or because they cannot smell it.

Addressing this mystery from several angles, scientists from the Monell Center first used sophisticated sensory testing techniques to show that both explanations apply: approximately eight percent of the subjects tested did not produce the odorous substance, while six percent were unable to smell the odor. One person both did not produce the odor and was unable to smell it.